It seems to me clearly "thank you", but i have another question. I suppose that, after this theatre, nobody should have played the King. What should have happened if, at the end, declarer played low and South played the Queen and another heart for North's Ace?

It's a very good work. I read (too quickly) the principles, and i have a question, that maybe it's already answered in the principles: what about the case in which everybody play 4♥ down 1 and I'm the only one who plays 3NT made? Which are ...